Combined AOPs for Formaldehyde Degradation Using Heterogeneous Nanostructured Catalysts

Abstract

In this paper we studied the combination of advanced oxidation processes (AOPs), i.e., TiO2-based photocatalysis and photo-Fenton process, on the degradation of aqueous solutions containing a low (90 ppm) concentration of formaldehyde. Heterogeneous nanostructured catalysts, supported on polymeric nanofibers, were used; for comparison, some homogeneous or partly heterogeneous systems were also analyzed. Furthermore, to make the process more sustainable (in terms of costs and safety) no hydrogen peroxide was added to the system. The results showed that the combination of AOPs gave a synergy since the presence of iron was beneficial in promoting the photocatalytic activity of TiO2 while TiO2 was beneficial in promoting the photo-Fenton reaction. Moreover, very good results were obtained using fully heterogeneous nanostructured catalysts (based on TiO2 and FeSO4), without the need to add H2O2.

Photocatalytic Advanced Oxidation Processes for Water Treatment: Recent Advances and Perspective

“…[30,31] In addition, with the reduction of Fe (III) by photo-generated electrons, the consumption of H 2 O 2 used to reduce Fe (III) can be decreased, thus promoting the effective utilization of H 2 O 2 . [32] As reported by Cui et al, [31] iron was fixed in-situ on a g-C 3 N 4 skeleton via forming σ-π coordinate bonds, to produce a kind of Fe-doped Fe-g-C 3 N 4 catalyst. The bonds allowed electrons to be quickly conveyed to Fe 3 + so as to form Fe 2 + .…”

“…And the whole Fenton process, as an electron acceptor, can also reduce charge carrier recombination in a photocatalyst, resulting in simultaneous desirable synergistic effects . In addition, with the reduction of Fe (III) by photo‐generated electrons, the consumption of H 2 O 2 used to reduce Fe (III) can be decreased, thus promoting the effective utilization of H 2 O 2 …”

Catalytic Oxidation of Ponceau 4R in Aqueous Solution using Iron-impregnated Al-pillared Bentonite: Optimization of the Process

“…Calibration curves for TOC was obtained using standard solutions of potassium hydrogen phthalate (C8H5KO4, ≥99.5%, Merck, Darmstadt, Germany), with a detection limit of 4 µg/L. TOC removal was determined by the Equation ( 6): (6) where TOC0 and TOCf are the total organic carbon concentrations at t = 0 and at the end of reaction (t = 5 h). Iron leaching of the catalysts after 5 h of reaction was measured with a Thermo Scientific iCE 3000 Series atomic absorption spectrometer.…”

“…Among the metals that are able to activate H2O2 and produce hydroxyl radicals in water, iron is the most frequently used. In the so-called Fenton process, H2O2 reacts with Fe 2+ ions to generate strong reactive species [5,6]. The generally accepted free radical chain mechanism for the Fenton reaction is summarized in Equations ( 1)-( 3), while the slow reaction (Equation ( 2)) becomes a rate-determining step of the Fenton reaction [7][8][9]:…”

Tandem Structures Semiconductors Based on TiO2_SnO2 and ZnO_SnO2 for Photocatalytic Organic Pollutant Removal

“…Advanced oxidation processes (AOPs) are considered as future alternative to traditional methods of removing organic pollutants: pharmaceutical active compounds [ 28 , 29 ], pesticides [ 30 , 31 ], dyes [ 32 , 33 ], volatile organic compounds [ 34 , 35 ], etc. The sustainability represents an important advantage of AOPs due to the use of light radiation as the main energy source to provide oxidative species responsible for pollutant mineralization [ 36 , 37 , 38 ].…”